Insulation, Radiant and Vapor Barriers - vinyl siding over old wood

I have 100 year-old home. Previous owner put vinyl siding directly over old wood siding. Inside walls are lath and plaster. There may be tar paper under old wood siding but I am sure there is no TYVEK, and little to no insuloation. these walls are very cold in winter. Should I insulate from the inside, taking out old lath and plaster, or from the outside-taking off vinyl, old lapbpard and going that way? It is a dilemma for a guy without:confused::confused: a lot of money.

The vinyl siding is easy to open up. You can remove as necessary, drill, and blow in insulation. Then plug and replace the siding and you are all set. Only if your plaster inside is in bad shape and needs replacing would I suggest going that way. I would suggest cellulose as it will air seal as well as insulate.

Bud

i just recently insulated my house (plaster and lathe) from the inside. i know the arguments to do it from the outside, but i drilled holes in the plaster and shot in an expanding foam. i found a slow rise formula and it worked fantastic. it is also closed cell so acts as a vapor barrier as well. the fact that it expands was reassuring... i really knew it was getting everywhere.

i don't like the loose fill stuff because 1. i don't trust that it fills all the voids, 2. you're still without a vapor barrier, and 3. it settles over time.

If you go from the inside, you will need to spackle, and repaint everything when its all done. You're going to need to repaint you're exterior when you get the vinyl off, so thats an argument for going from the outside.

i've got a bunch of pictures of the process, the product i used (there are other manufacturers), etc... if you're interested. it cost about 650 for 50 cubic feet, so if you know your cavity space you can get a good estimate of the cost (minus spackle, paint).

That sounds like a much easier way to go. Thanks. Since you can't see what is going on behind the holes and inside the walls, how do you know the EPS isn't leaving voids? Just curious.

Many thanks to Bud9051 and MSKIN for prompt and knowledgeable replies I can see under the vinyl siding and the old wood siding is pretty corrupt. I don't want to have to take it off if I don't have to--put up waferboard and tyvek, etc.

i used tiger foam slow rise formula. there are a few other competitors that i could have just as easily chosen. TF had decent customer support. they have a product demo video online you can check out.

The instructions tell you to drill 2 holes, due to my unique wall construction they recommended more (1/2" gwb on 1/2" rigid on 3/4 plaster and lathe). it was difficult to get the nozzle through a 1 3/4 finish assembly.

regardless, i would spray the bottom hole for a few seconds. ten seconds after releasing the trigger it was shooting out of the wall 2 feet up. it squeezed trough a couple of outlets, and i found locations in the basement where it squeezed through the sill plate.

my personal opinion is that the complete seal it provided was far greater value than the additional R9 i achieved. again, i only had an 1 1/2" - 2" void to fill.

word of caution, the high rise formulas can bulge your interior gwb. This is why to go with the slow rise, the total increase in volume is less and it rises slower. you will be fine however because you have the added reinforcing of the lath system. I drilled 1 1/8" holes instead of the 5/8" holes they recommend - again due to the depth of the finish layer.

mskin - I will look at the PDF instructions for use and cost on Tiger Foam. Sounds like a good product. Our plaster is in VG condition and should take the pressure w/o bowing.